CVE-2018-12291

Severity: high (CVSS 7.5 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2018-06-13 · updated 2026-06-17

Description

The on_get_missing_events function in handlers/federation.py in Matrix Synapse before 0.31.1 has a security bug in the get_missing_events federation API where event visibility rules were not applied correctly.

Affected products

matrix-org synapse: before 0.31.1 — fixed in 0.31.1

How to fix

Upgrade to a fixed version: matrix-org synapse 0.31.1. Check the vendor advisory for mitigations.

References

https://github.com/matrix-org/synapse/pull/3371
https://github.com/matrix-org/synapse/releases/tag/v0.31.1
https://github.com/matrix-org/synapse/pull/3371
https://github.com/matrix-org/synapse/releases/tag/v0.31.1

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